The present invention relates to a thermoplastic resin composition, more specifically a thermoplastic resin composition useful for composite molded articles such as automobile moldings.
Automobile parts, building parts and light electrical appliance parts were prepared by composite molding, e.g., by two-color molding, multiple different resins. Such composite molded automobile parts include window flames and lamp packing, building parts include sash flames, and light electrical appliance parts include push buttons for telephones, wireless installations, TV remote controllers and VTR remote controllers.
In general, parts are separately molded from each different resin and bonded with each other by an adhesive, or male part and female part are molded from different resins and fit into each other to obtain a composite molded article composed of multiple different resins.
However, the method with an adhesive has drawbacks that costs are high due to a complicated step of applying an adhesive and a skill is required to apply an adhesive effectively. The method of providing parts to be fit into has drawbacks that a necessary complicated mold raises costs and a fitting-into step worsens workability.
Then, it was proposed that parts from specific resins are heat bonded with each other to make a composite article, as described in Japanese Patent Application Laid-Open Nos. Sho-61-213145/1986, Sho-63-115711/1988, Hei-1-139240/1989, Hei-1-139241/1989, and Hei-2-139232/1990. However, it is difficult to control softness of the articles made from any of the compositions described in those publications. It is usually done to add an oil for easier control of softness of molded articles. However, if an oil is added to the aforesaid previous compositions, it is observed that the oil bleeds out from the surface of the resultant molded article or from the interface between the resins. Accordingly, bonding strength between the resins is week. Therefore, the molded article causes coming-off after a prolonged use.
In composite automobile moldings such as window moldings, roof moldings, protector moldings, weather moldings, and strip moldings, parts which are exposed outside must be resilient and excellent in anti-scratch resistance, weatherability and chemical resistance. Recently, olefin resins and styrene resins are used for those automobile moldings. However, those have a very strong restoring force against bend and, therefore, it is very difficult to bend and fit those into automobiles. In addition, the surface is easily scratched, so that beautiful gloss cannot be attained.
Hard olefinic polymers such as oinomers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-acrylic acid ester copolymers, and ethylene-methacrylic acid ester copolymers, are used in the surface skin layer of moldings to successfully improve anti-scratch resistance, weatherability and chemical resistance, as described in Japanese Utility Model Application Laid-Open Nos. Hei-5-32152/1993 and Hei-7-26217/1995. However, when a thermoplastic elastomer composition which has a weak restoring force against bend is used in a substrate, the surface layer composed of the hard olefinic polymer does not well bond to the substrate and comes off.
In various composite molded articles, a thermoplastic elastomer composition is desired to have good heat adhesion with various resins. Previously, polyolefinic thermoplastic elastomers (TPO) can be heat bonded to homologous polyolefinic resins, but are difficult to be heat bonded to ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers and oinomers which have a polar group. This is problematic in broadening its applications. Particularly in automobile lace parts, if TPO is used as a core material, only polyolefinic resin can be used as a surface skin, so that there is a limitation on resins to be used.
Accordingly, a purpose of the present invention is to provide a resin composition which has excellent mechanical properties and shows excellent heat adhesion with various resins, and further shows no bleeding of a softening agent and, therefore, allows easier control of softness of a molded article, and a layered molded article having a layer composed of this resin composition.
The present inventors have now found that the aforesaid purpose is attained by blending the following components (a) through (f) in the specified amounts.
Thus, the present invention is a thermoplastic resin composition comprising
(a) 100 parts by weight of a resin selected from the group consisting of polypropylenes and copolymers composed mainly of propylene,
(b) 5 to 350 parts by weight of a resin selected from the group consisting of polyethylenes and copolymers composed mainly of ethylene, the resin having been prepared using a single site catalyst,
(c) 5 to 200 parts by weight of a resin selected from the group consisting of
(c-1) ethylenic ionomer resins, and
(c-2) polymers and copolymers of 100 to 5% by weight of a monomer represented by the following formula (I):
CH2xe2x95x90C(R1)xe2x80x94COOR2xe2x80x83xe2x80x83(2)
xe2x80x83wherein R1 represents a hydrogen atom or a methyl group, and R2 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, with 0 to 95% by weight of ethylene,
(d) 0 to 200 parts by weight of a resin selected from the group consisting of polyethylenes and copolymers composed mainly of ethylene, precluding those prepared using a single site catalyst,
(e) 0 to 400 parts by weight of a block copolymer consisting of at least two polymeric blocks (A) composed mainly of a vinyl aromatic compound and at least one polymeric block (B) composed mainly of a conjugated diene compound, or a hydrogenated block copolymer obtained by hydrogenating said block copolymer, and
(f) 0 to 500 parts by weight of a non-aromatic softening agent for rubber.
In a preferred embodiment, the composition comprises 10 to 250 parts by weight of the resin (b) selected from the group consisting of polyethylenes and copolymers composed mainly of ethylene having been prepared using a single site catalyst.
In another preferred embodiment, the composition comprises 10 to 200 parts by weight of the resin (b) selected from the group consisting of polyethylenes and copolymers composed mainly of ethylene having been prepared using a single site catalyst.
In another preferred embodiment, the resin (b) selected from the group consisting of polyethylenes and copolymers composed mainly of ethylene having been prepared using a single site catalyst, is an ethylene-octene copolymer.
In another preferred embodiment, the composition comprises 10 to 180 parts by weight of the resin selected from the group consisting of components (c-1) and (c-2).
In another preferred embodiment, the composition comprises 10 to 150 parts by weight of the resin (d) selected from the group consisting of polyethylenes and copolymers composed mainly of ethylene, precluding those prepared using a single site catalyst.
In another preferred embodiment, the composition comprises 30 to 350 parts by weight of the block copolymer (e) consisting of at least two polymeric blocks (A) composed mainly of a vinyl aromatic compound and at least one polymeric block (B) composed mainly of a conjugated diene compound, or a hydrogenated block copolymer obtained by hydrogenating said block copolymer.
In another preferred embodiment, the composition comprises 40 to 200 parts by weight of the non-aromatic softening agent for rubber (f).
Another aspect of the invention is a laminated article comprising a layer of the above thermoplastic resin.
Another aspect of the invention is a laminated article comprising a layer of the above thermoplastic resin and a layer of one or more resins selected from the group consisting of polar resins selected from the group consisting of ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-acrylic acid ester copolymers, ethylene-methacrylic acid ester copolymers, ethylene-vinyl acetate copolymers, saponified ethylene-vinyl acetate copolymers and ionomer resins, and non-polar resins selected from the group consisting of non-polar polyolefinic resins and non-polar polystyrenic resins.
In a preferred embodiment, the non-polar polyolefinic resins include polypropylenes, propylene-xcex1-olefin copolymers, polyethylenes, ethylene-xcex1-olefin copolymeric rubbers, polybutenes, polyisobuthylenes, polybutadienes (BR), poly-4-methylpentene-1 resins, and olefinic thermoplastic elastomers.
In another preferred embodiment, the non-polar polystyrenic resins include polystyrenes, styrenic copolymeric rubbers, and styrenic thermoplastic elastomers.
In another preferred embodiment, the styrenic copolymeric rubbers include SBR, SBS, SIS, SIBS, SEBS, and SEEPS.
Another aspect of the invention is a shaped article having a core comprising the above thermoplastic resin composition, a surface layer of a polar resin and a lip of a non-polar resin.
In a preferred embodiment, the polar resin is selected from the group consisting of ethylene/acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-acrylic acid ester copolymers, ethylene-methacrylic acid ester copolymers, ethylene-vinyl acetate copolymers, saponified ethylene-vinyl acetate copolymers and ionomer resins, and the non-polar resin is selected from the group consisting of non-polar polyolefinic resins and non-polar polystyrenic resins.
In another preferred embodiment, the polar resin is an ionomer resin and the non-polar resin is a polyolefinic thermoplastic elastomer or a styrenic thermoplastic elastomer.
In another preferred embodiment, the article is a molding for automobiles.
In another preferred embodiment, the molding for automobiles is a window molding, a roof molding, a protector molding, a weather molding or a strip molding.